Physics: mesh moving on top of of another
If you really do not need the Physics simulation, you could use a Shrinkwrap constraint. To use a shrink wrap constraint, Add an empty, then  parent the empty to the ball (Ctrl P). Then add a Shrinkwrap constraint to the empty. Set the Shrinkwrap Target to the ground. For your case, you could set the Shrinkwrap Type to Project, then set it to -Z.



Keyframe your ball. Set the ball as a active rigid body (Add Active), in the Physics tab of the Tool Shelf. Then on your ground plane set it to a passive rigid body(Add Passive) in the Physics tab of the Tool Shelf. Play the animation from the beginning Shift Left arrowto jump to the beginning, and Alt A to play.